Biopsychology & its research methods

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Transcript of Biopsychology & its research methods

Applying principles from biology to the study of physiological, genetic and developmental mechanisms of behaviour in humans and non-humansDetermining the relationship between psychological processes and underlying biological events Biopsychology & its research methods Four levels of biological explanations of behaviour Conclusion 1. Causal The concept of reductionism is highly debatedThere are many techniques for measuring brain function, all with strengths and limitationsThe ideal is to use multiple techniques to gain convergent dataEthical point: what happens if an abnormality is found? Relating a behaviour to the activity of the brain and other organs 2. Developmental/ontogenetic Describing how a structure or behaviour develops, which includes genetic, nutrition and environmental influences 3. Evolutionary/phylogenetic Reconstructing the evolutionary history of a behaviour or structure 4. Functional Describing why a structure evolved as it is, determining its purpose Brain damage Process of reducing behaviour down to the behaviour of neurons and chemicalAn approach to understand more complex things by breaking them down into more fundamental partsThis helps to establish cause & effect but it doesn't tell us everything, we need to remember the whole picture Reductionism To Reduce or Not to Reduce Emergent Properties The result of several processes working together to form a more complex behaviourThese therefore cannot be reducedAn example is consciousness: there's no one part of the brain responsible for it, it's the product of many. If one part was removed, consciousness would suffer but not necessarily noticeably Research Methods Yay? Can be caused by:Accidents'Natural pathology' (tumours, strokes)Therapeutic interventions (surgery e.g. removing tumour)Experimental damage in the case of nonhuman animals (e.g. lesions, ablasions)It can also be emulated by stimulating a specific site of the brain (chemically or electrically) and triggering the behaviour, unlike lesions which damage it and therefore disrupt it. One example of this is transcranial magnetic stimulation (TMS) which uses a powerful magnetic field to stimulate part of the brain. Pros: Useful for finding out specific areas involved in certain tasksUseful for studies of 'before and after' surgery as there is more control for comparing behaviour in same person Cons With 'before and after' studies, there must have been an abnormality present for surgery to be neededLocalised lesion + functional deficit ≠ that region responsible for the functionMight be that the lesion is in the pathway to the actual regions responsible for the functions Electroencephalography (EEG) Electrodes are attached to the scalp detecting electrical activity in the brain. It takes advantage of the fact that neurons release voltage signals when communicating. However, single neurons are too small so it measures the average for a group. Pros Gives an overall picture of the brain's electrical activityGood temporal resolution (very quick)Relatively cheap and easy to set upNon-invasive Cons Spatial resolution (how accurate an area) is not very preciseHard to record deeply (distance)Electrical so very easily disturbedCan take a long time to set up participants (when done properly) Neuroimaging Two categories:1. Structural/anatomical neuroimaging: looks at the anatomy of the brain in terms of sizes & locations of different regions etc. It helps to identify structural abnormalities which might then be related to behavioural manifestation2. Functional neuroimaging: looks at the brain in action. Abnormality can be identified in terms of unusual patterns of under-/over-activity in a brain region MRI AnatomicalSubstances that make up the body have intrinsic magnetic properties and react when is applied FMRI Measures changes in BOLD signal (blood oxygen level dependent signal)Deoxygenated blood distorts magnetic field so shows which areas of the brain are in useGood functional informationHigh temporal resolutionNon-invasivePoor spatial resolutionLimitations on stimulus presentation (very loud so hard for auditory studies)No magnetic metallic objects can be nearDoesn't directly measure brain activity, it looks at areas blood is being directed to and assumes they're being used, therefore it's a proxy for brain activityRelatively large area (activity in 1 voxel = 4.5m neurons) Positron emission tomography (PET) Reveals differences between brain regions in their blood flow, metabolism of fuels or presence of substances (such as a particular neurotransmitter)Injects radioactive chemicals and measures the emission from the radioactive decay processPositrons are released when decaying which are mutually destroyed upon meeting an electron, emitting 2 gamma rays which travel in opposite directionsThe detector picks this up and works out the middle point where it occurredThe radioactive chemical used is a form of glucoseSo if there's a lot of gamma rays, then there's a high concentration of the radioactive glucose thereThis suggests this part of the brain is very active (as it needs more energy) Animal studies The underlying mechanisms of behaviour are similar across speciesIt's easier to study animalsLearning about animals can shed light on human evolutionProblems with legal and ethical restrictions

Lesion studies:Don't have to wait for it to happen naturallyMore controlGenetic studies:Quicker to breed so can test for genetic effects over quite a short timescale Minimalists: tolerate some kinds of animal research but wish to prohibit others, depending on the probable value of the research, distress caused and animals usedAbolitionists: believe animals have the same rights as people so since they cannot give consent, we shouldn't use them